As one example of a vehicular drive system arranged to transmit an output of an engine to drive wheels of a vehicle, there is known a drive system including a power distributing mechanism arranged to distribute the output of the engine to a first electric motor and an output shaft, and a second electric motor disposed between the output shaft of the power distributing mechanism and the drive wheels. Examples of this type of drive system include hybrid vehicle drive systems disclosed in Patent Documents 1, 6 and 8. In these hybrid vehicle drive systems, the power distributing mechanism is constituted, for example, by a planetary gear set which functions as a differential mechanism a differential action of which permits a major portion of a drive force of the engine to be mechanically transmitted to the drive wheels, and the rest of the drive force to be electrically transmitted from the first electric motor to the second electric motor, through an electric path therebetween, thereby making it possible to drive the vehicle with the engine kept in an optimum operating state with an improved fuel economy. Where a step-variable transmission is provided between a power transmitting member and the output shaft, a torque to be transmitted to the power transmitting member is boosted, making it possible to reduce the size of a drive power source including the electric motors.
[Patent Document 1] JP-2003-127681A
[Patent Document 2] JP-11-198670A
[Patent Document 3] JP-11-198668A
[Patent Document 4] JP-11-217025A
[Patent Document 5] JP-WO 03/016749A1
[Patent Document 6] JP-2003-130202A
[Patent Document 7] JP-2003-130203A
[Patent Document 8] JP-2000-2327A